docs: def add_gene_family_to_graph(self, family_id):
          """
          Make an association between a group of genes and some grouping class.
          We make the assumption that the genes in the association
          are part of the supplied family_id, and that the genes have
          already been declared as classes elsewhere.
          The family_id is added as an individual of type DATA:gene_family.
  
          Triples:
          <family_id> a EDAM-DATA:gene_family
          <family_id> RO:has_member <gene1>
          <family_id> RO:has_member <gene2>
  
          :param family_id:
          :param g: the graph to modify
          :return:
          """
          family = Family(self.graph)
          gene_family = self.globaltt['gene_family']
  
          # make the assumption that the genes
          # have already been added as classes previously
          self.model.addIndividualToGraph(family_id, None, gene_family)
  
          # add each gene to the family
          family.addMember(family_id, self.sub)
          family.addMember(family_id, self.obj)
  
          return